Synergistic effect of silica sand particle size on the compressive strength and pore structure of geopolymers prepared from recycled fired clay brick waste

This research explores the synergistic effect of adding silica sand powders of various particle sizes (45, 63, 125 and 200 μm) to un-burnt and burnt recycled fired-clay brick wastes. The study examines the impact of the powders of silica sand on the compressive strength and microscopic pore structure of geopolymers. The addition of 4 wt% of each particle size of silica sand powder was separately incorporated into each recycled fired-clay brick waste that had been sieved at 125 μm. The strength values of the reference geopolymers made from un-burnt and burnt recycled fired clay brick waste without silica sand addition are 40.96 MPa and 53.16 MPa, respectively. Geopolymers from un-burnt and burnt recycled fired clay brick wastes have compressive strengths of between 40.29 and 50.88 MPa and between 45.75 and 64.89 MPa, respectively, when silica sand powders with the particle sizes are increased from 45 to 125 μm. Geopolymers from un-burnt and burnt recycled fired clay brick wastes achieve their maximum compressive strengths when the silica sand powder added is sieved at 125 μm. Pore structure examination reveals that all geopolymers have mesopores and macropores in their structure. The compressive strength and pore structure of geopolymers were found to be affected by silica sand with different particle sizes that is added to recycled-fired clay brick wastes that have been sieved at 125 μm.